Joe Flacco wearing knee brace, participating in light practice

Aaron WilsonThe Baltimore Sun

Although the Ravens left little doubt that quarterback Joe Flacco will line up Sunday against the New England Patriots despite an minor sprained left knee, he won’t do so without taking a precautionary measure.

A magnetic resonance imaging exam revealed that Flacco suffered a low-grade sprain of his medial collateral ligament, according to a source.

Consequently, Flacco will wear a protective brace on his knee Sunday for the first time in his NFL career after being fitted for the equipment and started using it Wednesday during a light workout where he wasn’t limping noticeably.

“I don’t know if it will be a necessity or not, but I’m going to wear it,” said Flacco, who hasn’t worn a brace since his junior year at Delaware when he sprained his left medial collateral ligament. “There’s no reason not to. The brace isn’t a big deal. Hopefully, it will prevent anything really crazy from happening if I happen to get hit on it again.”

Flacco practiced on a limited basis, taking snaps and handing off to running backs during the portion open to reporters. He didn’t seem to have any major issues with his mobility or appear to be in pain.

“It has been pretty stiff,” said Flacco, adding that he doesn’t expect the knee to need to be addressed after the season. “It’s feeling better, though. It looks like it’s getting better and better. Hopefully, some of the swelling will go down and stuff like that. So, yes, it’s getting better. That’s a good sign I think.”

Flacco got hurt in the second half of the Ravens’ 18-16 victory Monday night against the Detroit Lions when linebacker DeAndre Levy crashed into his knee.

Ravens coach John Harbaugh said he’s already spoken with league officials about why the play didn’t draw a penalty under an NFL rule that protects quarterbacks from low hits. Levy could draw a fine from the NFL.

“I got an explanation on the field,” Harbaugh said. “I got a different one from the league office. They’re going to send it up for discipline, and we’ll just have to see what the league does with it.”

The NFL adopted the rule to further protect quarterbacks after former Ravens strong safety Bernard Pollard knocked Patriots quarterback Tom Brady out for the 2008 season with a low hit that tore knee ligaments.

“It should have been a penalty,” Ravens strong safety James Ihedigbo said of Levy’s hit. “For the refs to miss something so blatant like that, it’s unacceptable. If a quarterback gets hit below the knee, that’s what the rule is there for.”

Harbaugh acknowledged that the blow Flacco absorbed concerned him greatly Monday night, and he was relieved he wasn’t hurt seriously.

“I winced when I saw it up on the board and I tried to talk to the referee about it and explain to him what had happened,” Harbaugh said. “I wasn’t sure if he saw it. He said he did. I winced when I saw it on tape again. It was a pretty tough hit. I remember a few shots that he’s taken to the lower body and to the knee. I don’t think I remember him taking one that bad.”

Meanwhile, tight end Dallas Clark didn't practice due to an illness. He's been under weather for the past few days.

Cornerback Asa Jackson (hamstring), who left the game and didn't return Monday, isn't practicing as well as linebacker Albert McClellan. McClellan has a stiff neck.

Running back Ray Rice didn't practice due to a minor thigh injury, but was walking fine after the game.